Possible Clues:

• Origin's English, showing root
• Drinks, say, containing trace of natural stimulant
• Root with therapeutic properties
• Medicinal aromatic root
• Herbal remedy gives new endless drive in performance
• Nag about nines when one over the eight, stimulating stuff
• Plant tuber credited with tonic properties
• Shorts with English tonic
• Chinese medicinal root
• What may restore fount of knowledge from King's, after playing with some appropriate language